gpiolib: never report open-drain/source lines as 'input' to user-space

From: Bartosz Golaszewski <[email protected]>

If the driver doesn't support open-drain/source config options, we emulate this behavior when setting the direction by calling gpiod_direction_input() if the default value is 0 (open-source) or 1 (open-drain), thus not actively driving the line in those cases.

This however clears the FLAG_IS_OUT bit for the GPIO line descriptor and makes the LINEINFO ioctl() incorrectly report this line's mode as 'input' to user-space.

This commit modifies the ioctl() to always set the GPIOLINE_FLAG_IS_OUT bit in the lineinfo structure's flags field. Since it's impossible to use the input mode and open-drain/source options at the same time, we can be sure the reported information will be correct.

---
 drivers/gpio/gpiolib.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

index f497003f119c..80a2a2cb673b 100644
@@ -1091,9 +1091,11 @@ static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
 			lineinfo.flags |= GPIOLINE_FLAG_ACTIVE_LOW;
 		if (test_bit(FLAG_OPEN_DRAIN, &desc->flags))
-			lineinfo.flags |= GPIOLINE_FLAG_OPEN_DRAIN;
+			lineinfo.flags |= (GPIOLINE_FLAG_OPEN_DRAIN |
+					   GPIOLINE_FLAG_IS_OUT);
 		if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
-			lineinfo.flags |= GPIOLINE_FLAG_OPEN_SOURCE;
+			lineinfo.flags |= (GPIOLINE_FLAG_OPEN_SOURCE |
+					   GPIOLINE_FLAG_IS_OUT);
 
 		if (copy_to_user(ip, &lineinfo, sizeof(lineinfo)))
 			return -EFAULT;

2.21.0

Patch applied for fixes!
Good catch.

Yours,
Linus Walleij